The purpose of the muscle energy converter (MEC) is to efficiently convert the power of linear muscle contractions into a form which can be used by a variety of implanted hydraulic actuators, including ventricular assist devices. The objective is to eliminate the need for external power supplies which contribute significantly to infection and device failures.
Considerable progress has been made over the last 30 years toward the development of implantable circulatory assist devices, but some fundamental problems still remain. No device in existence can provide both the reliability and unobtrusiveness required of a chronic implantable blood pump due, in large part, to the lack of a suitable power source. Current systems employ external power supplies with energy transmitted across the skin via tubes, wires, or electromagnetic fields. These schemes work well for short-term applications, but are not well-suited for chronic use due to infection and mechanical failure. However, many of these problems would be eliminated if a simple, implantable energy source could be developed.
Research on a device designed to perform the same function as the MEC device described herein is currently ongoing at California Pacific Medical Center (see Reichenbach S. H., K. J. Gustafson, G. D. Egrie, J. R. Weidman, D. J. Farrar, and J. D. Hill. Evaluation of a skeletal muscle energy convertor in a chronic animal model. ASAIO J. 46:482-485, 2000). There are however, substantial differences in design between these two technologies which render them quite distinct. These important distinctions are evidenced by the separate US patents issued to ASRI on 2, Jan. 1996 (U.S. Pat. No. 5,479,946) and CPMC on 22 Aug. 1995 (U.S. Pat. No. 5,443,504).
Based on results from 3rd-generation muscle energy converter (MEC3) bench testing and initial implant trials, significant design changes have been implemented to improve both function and biocompatibility of this device. Potential drawbacks of the MEC3 design scheme were found to be the following: low bellows durability; high bellows volumetric compliance; high housing profile; exposed actuation head; and potential shaft sheathing porosity. The design modifications described herein are meant to achieve the following: a) improve bellows durability; b) reduce or eliminate bellows compliance; c) lower device profile; d) eliminate exposed piston head; and e) eliminate the need for flexible sheathing.